Many conventional chemical processes yield process waste streams comprising acid, e.g., sulfuric acid, and amines, e.g., organic tertiary amines. The amines are commercially valuable and, as a consequence, it is desirable to recover the amines from the waste stream.
As one example of amine recovery, DE 101 46 689 discloses a method that utilizes distillation to recover organic amines from a catalyst waste stream that contains the amines and other impurities. As another example, DE 35 22 470 A discloses the use of a caustic soda to recover amines and metallic components from a polyphenylene ether synthesis waste stream. Also, DE 44 16 571 discloses the recovery of amines from an acidic stream. The process of DE 44 16 571 utilizes the addition of alkali bases to the acidic stream followed by distillation.
As another example, CN 1883790 describes the recovery of amines from a sulfuric acid/amine waste stream by neutralization with inorganic bases of oxide origin, e.g., NaOH, KOH, Ca(OH)2, or CaCO3. The neutralization of the sulfuric acid may, via side reactions, yield the respective sulfate, e.g. calcium sulfate or sodium sulfate. These sulfates may be disposed of or, if the sulfates are valuable, may be processed in order to obtain a useful and/or saleable end product. The processing, e.g., evaporation or drying, however, requires large amounts of energy. Also, due to the molar masses of the oxides that are required by the stoichiometry of these reactions, large quantities of oxides must be used. When calcium bases are employed, the calcium sulfate that is created precipitates during the reaction and, as such, the reaction suspension must either be diluted or thoroughly blended, which adds to the separation cost.
In other conventional processes, ammonia may be utilized as the inorganic base in the recovery of the amines. In such cases, the recovery process yields a recovered amine product stream and a by-product stream that comprises ammonium sulfate. The ammonium sulfate has commercial value, e.g., as a fertilizer, and may be collected and sold or otherwise utilized. Solids, however, are known to form in these conventional by-product streams. The solids cause processing and/or quality control problems. For example, the solids may collect on the walls of process equipment, e.g., tanks or pipes, which creates the need for costly maintenance. In some cases, the solids may form during transportation and/or storage, which results in a delivered product that is unacceptable to end users.
Even though conventional amine recovery processes may produce an ammonium sulfate by-product, the need remains for an improved process that yields an ammonium sulfate by-product that forms little or no solid formation over time.
All of the references discussed above are hereby incorporated by reference.